Variable resistor contact blade tension adjusting means



R. P. PAGET April 21, 1959 VARIABLE RESISTOR CONTACT BLADE TENSIONADJUSTING MEANS 2 Sheets-Sheet 1 Filed Dec. 20, 1956 INVENTOR REGINALDF! PAGET BY S/ Z: w HTTUENEY R. P. PAGET 2,883,501

VARIABLE RESISTOR CONTACT BLADE TENSION ADJUSTING MEANS A ril 21, 1959 2Sheets-Sheet 2 Filed Dec. 20, 1956 IN VEN TOR. REGI LD R PAGET BY I LU4ND cud...

HTTOENE'Y United States Patent VARIABLE RESISTOR CONTACT BLADE TENSIONADJUSTING MEANS Reginald P. Paget, Costa Mesa, Calif., assignor to theUnited States of America as represented by the Secretary of the AirForce Application December 20, 1956, Serial No. 629,765

4 Claims. (Cl. 201-56) This invention relates to variable resistors suchas potentiometers and, more particularly, to means for adjusting thecontact pressure or tension between a stationary contact member and anadjustable contact spring in order to compensate for inaccuracies in theforming of the contact spring and variations in the contact tensionbetween the movable contact spring or blade and a stationary contactmember or ring.

A further object is the provision of a simple adjusting means disposedintermediate the opposite ends of an elongated flexible electricalcontact blade member and an adjustable support therefor for controllablybending a portion of the blade adjacent its supported end for adjustingthe free or outer contact end of the blade to regulate the contactingtension thereof with a cooperating stationary contact member.

A further object is the provision of a mounting support for an elongatedflat contact blade and means for controllably bending the blade betweenpredetermined points adjacent its supported end to adjust the freecontacting outer end of the blade to vary the contacting tension thereofon a circular stationary contact member.

A further object is the utilization of the tension adjusting means as ameans for securing the blade on the adjustable support and bending theblade adjacent the adjusting means to vary the contacting tension of thefree end of the blade on a stationary contact element.

A still further object involves reducing the crosssectional area of thecontact blade adjacent the adjusting means to decrease the stiffness ofthe contact blade in such area.

Another object includes the provision of means for supporting a flatresilient elongated contact blade transversely of its longitudinal axisat spaced points adjacent a fixed end thereof and means for adjustablyapplying pressure to the blade substantially midway between said spacedpoints to flex the free outer end of the blade in the opposite directionfor adjusting the contacting tension of the free end of the blade on acircular contact element.

Other objects and advantages of the invention will become apparent fromthe following description and accompanying drawings in which likereference characters refer to like parts in the several figures.

Figure 1 is a perspective view of a variable resistor incorporating theinvention, parts being broken away to more clearly illustrate theinvention, the casing being omitted.

Figure 2 is a fragmentary sectional view taken approximately on theplane indicated by line 2-2 in Fig. 1, looking in the direction of thearrows.

Figure 3 is a fragmentary sectional view taken approximately on theplane indicated by line 3-3 in Fig. 1, looking in the direction of thearrows.

Figures 4 and 5 are enlarged detail views of the contact blades shown inFigs. 2 and 3, respectively, forming part of the invention.

Referring more particularly to Fig. 1, the reference numeral 1 denotesan adjustment shaft, which is adapted 2,883,501 Patented Apr. 21, 1959to be journalled in suitable bearing in a casing not shown.Concentn'eally surrounding the shaft 1 is a circular or spiral shapedresistance coil element 2 comprising a plurality of turns 3 about thecentral axis of the shaft 1, said turns 3 of the resistance coil element2 being uniformly spaced apart a distance at least equal to thecrosssectional dimension of the resistance turn 3 of the coil 2 toprovide a space 5 between the coils 3 having a similar dimension as theresistance element.

A rotor 6 is carried by the shaft 1 and preferably splined thereto toturn about the axis of the shaft 1. The rotor 6 is formed with anelongated guide block portion 7 traversing the coils 3 in inwardlyspaced relation thereto.

A contact support element 8, formed with a guide channel 9 therein isslidably disposed on said guide block portion 7 for longitudinaladjustment between the rotor 6 and the convolutions of the resistancecoil 2. The support element 8 is formed with spaced outer guide elements10 and 11 extending into the space 5 between the convolutions of theresistance coil element and is formed with circular channels 12 and 13straddling the coils 3, the grooves or guide channels 12 and 13 engagingalternate turns or coils of the resistance element 2 and is providedwith an intermediate channel or space 14 disposed under the coil or turn3 located between the coils riding in the guide channels 12 and 13. Thisintermediate channel accommodates a resilient contact blade 15, with itsfree end 16 disposed in sliding contact with the inner surface of theresistance coil 2. The inner end 17 of the blade 15 is secured to theend face 18 of the slide block 8 and is inclined through the space orchannel 14 to dispose the free end 16 thereof in contact with the coil2.

A transverse groove or channel 19 extends transversely across the end18, as shown, with the inner end portion 17 of the contact blade 15spanning the groove 19 in contact with the end 18 at opposite sides ofthe groove 19.

The end portion of the contact blade is apertured at 20, substantiallyover the center of the groove 19, and tension adjusting means, such asan adjusting screw 21, is passed through the aperture 20, and threadedinto a threaded opening formed in the base of the groove 19substantially midway between its side walls, the head of the screwengaging the outer surface of the contact blade to tension the bladetoward the recess or groove 19. Adjustment of the screw 21 depresses theblade intermediate the supporting edges of the recess 19 to increase thetension of the free end of the blade 15 on the resistance coil 2.

A flexible conductor 22 connects the inner end 17 of the contact blade15 to a second adjustable resilient contact blade 23. This secondcontact blade 23 is secured at its lower or fixed end 24 to an insulatedsupport block 25 carried in a suitable complementary recess or notch 26formed in the rotor 6.

The upper or contact end of the second contact blade 23 is bifurcated toprovide spaced contacts 27 disposed at the upper end of the resilientblade portion 28 in equal radial displacement from the adjustment shaft1.

A fixed resilient contact blade 29 is suitably secured to the casing(not shown) and is offset at 30 to pass the end of the guide portion 7and carries a flat annular or ring portion 31 disposed to engage thecontact elements 27.

The portion of the ring 31 which engages the contacts 27 is fiat,circular and concentric to the shaft 1, having a terminal adapted to beconnected to one of a pair of electrical circuit conductors (not shown)while the other electrical input conductor is connected to one end ofthe resistance coil 2.

"sides of 'the notch. The opposite edge portions of the blade 23,between the opposite sides of the notch 32, are notched at 33 and alsoapertured at 34 substantially midway over the notch '32 to provide forgreater flexibility of the contact blade portion spanning the notch 32.An adjustment screw 35 extending through the aperture 34 into a threadedopening formed in the base of the notch 32, the head of the screwengaging the outersurface of the blade. Adjustment of the screw 35toward the notch 32 bends the portion of the blade 23 spanning the notchto move the contacts 27 of the blade into greater tensionin'gcontactwith the slip ring contact member 31.

Loosening of either the screw 35 or the screw 21 reduces the tensioningcontacts respectively of the free ends of the blades 24 or 15 on thering or resistance coil contacts 31 or '2.

The invention is shown and described in one embodiment for purposes ofillustration, it being obvious that changes may be made thereon by thoseskilled in the art without departing from the spirit and scope of theinvention as defined in the accompanying claims.

I claim:

1. -In a variable resistor, the combination of a resistance elementproviding a plurality of turns extending around an axis, there being aspace between adjacent turns of the same configuration as saidresistance element, a rotor journalled to turn about'said axis providinga channel traversing said turns, a'first contact means comprising asupport element slidable along said channel, a first resilient contactblade carried by said support element having a free end engaging a turnof said resistance element, tension adjusting means between said bladeand said support element for adjusting the tensional contact betweensaid blade and said turn of said resistance element, means for advancingsaid support element along said resistance element during rotation ofsaid rotor comprising a guide element carried by said support elementand extending into said space to follow the convolutions of saidresistance element, secondary contact means for establishing contactbetween one end of said resistance element and said first contact bladecomprising a stationary contact blade having an annular contact ringsurrounding said axis concentric thereto, an elongated resilient secondcontact blade secured at one end to said rotor in radially spacedrelation to said axis and having a free end disposed in contactingrelation with said contact ring, said rotor having a notch formedtherein adjacent the secured end of said rotor carried second contactblade transversely thereof with the blade spanning the notch in contactwith said rotor at oposite sides of said notch, and means for moving theportion of the blade spanning'the notch toward the notch to bend theblade to vary the tensional contact between the free end of said secondcontact blade and said contact ring.

2. A variable resistor as claimed in claim 1 in which said tensionadjusting means for said first contact means includes a notch formed insaid support element adjacent the end of the first contact'blade remotefrom said free end and transverse to said blade with said blade spanningsaid notch in contact with the support element at opposite sides of thenotch and means between said first contact blade and said supportelement intermediate the ends of the cooperating notch for bending saidfirst blade toward said notch for varying the tensional contact be tweenthe free end thereof and said resistance element.

3. Apparatus as claimed in claim 2, in which at least one of saidcontact blade portions spanning one of said notches is reduced incross-sectional area intermediate the ends of the notch which it spansto cause the bending thereof to occur substantially midway between theends of said notch.

4. Apparatus as claimed in claim 2 in which at least one of saidresilient contact blades is formed with an aperture intermediate thesides of the notches and the side edges of the blade, and a tensionadjusting screw threaded into the support element intermediate the sidesof the notch and having a head thereon engaging the outer face of theblade intermediate the sides of the notch toward the base 'of the notchfor bending the blade intermediate the'sides of the notch toward thebase of the notch.

References Cited in the file of this patent UNITED STATES PATENTS2,288,043 Stanton June 30, 1942 2,406,079 Krueger Aug. 20, 19462,454,986 Beckman Nov. 30, 1948 2,480,995 Armitage Sept. 6, 19492,486,931 Edwards et al Nov. 1, 1949 2,495,321 Gibbs et a1. Jan. 24,1950 2,558,326 Van Dyke June 26, 1951 2,813,182 Van Alen Nov. 12, 1957

